Methodology for modeling the EB-PVD coating process

Abstract

This paper presents a methodology for modeling and analyzing the Electron Beam-Physical Vapor Deposition (EB-PVD) coating process. The Knudsen (Kn) number for the current processing conditions is near but smaller than 0.1 so the continuum approach (based on Navier-Stokes equations) is still valid though the dilute gas regime is considered. The methodology developed in this work is applied to optimization of the evaporation and deposition rates and patterns of metal vapors on ceramic substrates. The methodology is based on the numerical solution of evaporation, fluid flow, species transfer, heat transfer, and a deposition/condensation kinetics model. The models developed for the analysis of the coating process include an ingot EB-melting/evaporation model, a computational fluid dynamics (CFD)-vapor distribution/plume dynamics model (chamber model), and a coating-kinetics model. Numerical simulations at the macro-level were conducted using CFD software. The results from the ingot EB-melting/evaporation model are used as input data in the CFD-vapor distribution model. The coating-kinetics model uses as input, data pressure, temperature, and concentration of Ti-6Al-4V (Ti-6-4) vapors computed with the CFD model. To account for the rarefied gas regime (where Knudsen number [Kn] could be larger than 0.1), appropriate low-pressure “boundary slip conditions” with momentum and thermal accommodation coefficients as a function of Kn were used. Numerical results for temperature and Ti-6-4 vapor concentration profiles in the chamber are presented. Experiments conducted at FMW Composite Systems Inc. are also presented.